1. Field of the Invention
This invention relates generally to valves used in the petroleum industry, and the like, and particularly to a pig valve for use with a pigging system of a pipeline in order to permit launching and receiving of a sphere or cylinder sent through the pipeline for the purpose of cleaning the interior surfaces of the pipe forming the line.
2. Description of the Prior Art
Petroleum products flowing through pipelines deposit substances on the walls or on the bottom of the pipe. Oil from the well deposits paraffin, which reduces the flow area and efficiency of the pipeline. Further, water and other liquids settle in low points of natural gas pipelines, forming similar obstructions to the flow of fluid through the line. Thus, it is common practice to insert a rubber "pig", which may be either a ball or cylinder, into the pipelines so that it can be pushed along by the fluid flow through the pipeline and will push ahead of it any foreign material which may obstruct flow through the line. The foreign material can be removed at the end of the line.
U.S. Pat. Nos. 3,125,116, issued Mar. 17, 1964 to B. P. Schaberg; 3,186,014, issued June 1, 1965 to H. Allen; 3,218,660, issued Nov. 23, 1965 to H. N. Eagleton; 3,246,355, issued Apr. 19, 1966 to D. A. VanScoy; and 3,473,550, issued Oct. 21, 1969 to D. A. VanScoy et al., disclose various devices for launching and receiving pigs in pipelines. Further, U.S. Pat. No. 3,035,640, issued May 22, 1962 to W. C. Gibson et al., discloses a Kelly cock for use in ball into a string of well pipe.
In general, the prior art pig valves require valve elements disposed transverse to the flow of fluid through the pipeline so as to at least partially block the fluid flow during pig launching and receiving operations. Further, the flow through the valve, or through accessory piping necessary for installation of the valve, often requires inefficient and expensive sharp turns in the flow path.